The present invention relates to an active matrix liquid crystal display device which is composed of an active matrix liquid crystal display element in which picture element electrodes are arranged in a matrix form in a liquid crystal cell and electric charges are charged into and discharged from the picture element electrodes by thin film transistors to provide a display, and a driver for driving the liquid crystal display element.
A conventional liquid crystal display element of this kind has such a structure as shown in FIG. 1, in which a pair of transparent substrates 11 and 12 as of glass are disposed opposite but adjacent each other, with a spacer 13 interposed between their marginal edges, and liquid crystal 14 is sealed in between the transparent substrates 11 and 12, constituting a liquid crystal cell 10. On the inside surface of the transparent substrate 11 a plurality of picture element electrodes 15 are provided and a thin film transistor 16 is disposed, as a switching element, adjacent each picture element electrode 15, the thin film transistor 16 having its drain connected to the picture element electrode 15. On the inner surface of the other transparent substrate 12 a transparent common electrode 17 is disposed in opposing relation to the plurality of picture element electrodes 15.
As shown in FIG. 2, the picture element electrodes 15 square in shape are arranged in a matrix form on the transparent substrate 11, a gate bus 18 is disposed adjacent and along each row arrangement of the picture element electrodes 15, and a source bus 19 is similarly disposed adjacent and along each column arrangement of the picture element electrodes 15. At each intersection of these gate and source buses 18 and 19 the thin film transistor 16 is provided, which has its gate connected to the gate bus 18, its source connected to the source bus 19 and its drain connected to the corresponding picture element electrode 15.
By applying voltage across selected ones of the gate and source buses 18 and 19, only that one of the thin film transistors 16 to which the voltage is applied is conducted, charging the picture element electrode 15 connected to the drain of the conducted thin film transistor 16. As a result, a voltage is applied across the liquid crystal 14 only between the charged picture element electrode 15 and the common electrode 17, by which only that portion of the liquid crystal 14 is made transparent or opaque, thus providing a selective display. The display can be erased simply by discharging the stored charges from the conducted picture element electrode 15.
For such selective control of the thin film transistors 16, a plurality of outputs of a gate driver 21 which is able to drive the gate buses 18 individually are connected thereto and outputs of a source driver 22 are connected to the source buses 19, respectively.
A one-latch-type source driver typically used as the source driver 22 is simple-structured, but when the product of the source input capacitance value and the resistance value between adjacent source buses is small, crosstalk will be produced between the source buses 19, leading to the deterioration of the display characteristic such as lowering of the contrast of a display.